cut_mesh return indices?

[darikg]

The c++ cut_mesh has a third output I: V by 1 list of the map between Vn to original V index.

It'd be nice to have this in the python wrapper. It looks like an easy change to make but harder to make backwards compatible. Would adding an optional kwarg return_index=False be acceptable?

[alecjacobson]

return_index kwarg seems like a great idea.